Resin material, endless belt for image forming apparatus, roller for image forming apparatus, image fixing device, and image forming apparatus

ABSTRACT

A resin material used for a member for an image forming apparatus includes a polymer formed by polymerization of at least one acrylic resin in which a content ratio (molar ratio) of hydroxyl groups of side chains each containing 10 or more carbon atoms to hydroxyl groups of side chains each containing less than 10 carbon atoms is less than 1/3; at least one polyol that contains plural hydroxyl groups in which all the hydroxyl groups are connected together through a chain containing 6 or more carbon atoms; and an isocyanate, with a polymerization ratio of about 0.1 or more and about 10 or less, the polymerization ratio being a ratio (B/A) of a total molar amount (B) of hydroxyl groups contained in all the polyols used for the polymerization to a total molar amount (A) of hydroxyl groups contained in all the acrylic resins used for the polymerization.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2010-029211 filed Feb. 12, 2010.

BACKGROUND

(i) Technical Field

The present invention relates to a resin material, an endless belt foran image forming apparatus, a roller for an image forming apparatus, animage fixing device, and an image forming apparatus.

SUMMARY

According to an aspect of the invention, there is provided a resinmaterial used for a member for an image forming apparatus, the resinmaterial including a polymer, wherein the polymer is formed bypolymerization of at least one acrylic resin in which a content ratio(molar ratio) of hydroxyl groups of side chains each containing 10 ormore carbon atoms to hydroxyl groups of side chains each containing lessthan 10 carbon atoms is less than 1/3 (the acrylic resin may contain nohydroxyl group of a side chain containing 10 or more carbon atoms); atleast one polyol that contains plural hydroxyl groups in which all theplural hydroxyl groups are connected together through a chain containing6 or more carbon atoms; and an isocyanate, with a polymerization ratioof about 0.1 or more and about 10 or less, the polymerization ratiobeing a ratio (B/A) of a total molar amount (B) of hydroxyl groupscontained in all the polyols used for the polymerization to a totalmolar amount (A) of hydroxyl groups contained in all the acrylic resinsused for the polymerization.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a perspective view schematically illustrating theconfiguration of an endless belt according to an exemplary embodiment;

FIG. 2 is a sectional view of an endless belt according to an exemplaryembodiment;

FIG. 3 is a schematic view illustrating the configuration of an imageforming apparatus including an endless belt according to an exemplaryembodiment;

FIG. 4 is a schematic view illustrating the configuration of an imagefixing device including an endless belt according to an exemplaryembodiment;

FIG. 5 is a schematic view illustrating the configuration of an imagefixing device including an endless belt according to another exemplaryembodiment; and

FIG. 6 is a schematic view illustrating the configuration of an imageforming apparatus including an endless belt according to an exemplaryembodiment, the endless belt serving as a paper-sheet transport belt.

DETAILED DESCRIPTION Resin Material Used for Member for Image FormingApparatus

A resin material used for a member for an image forming apparatusaccording to an exemplary embodiment includes a polymer formed bypolymerization of

at least one acrylic resin in which a content ratio (molar ratio) ofhydroxyl groups of side chains each containing 10 or more carbon atoms(long side chain hydroxyl groups) to hydroxyl groups of side chains eachcontaining less than 10 carbon atoms (short side chain hydroxyl groups)is less than 1/3 (the acrylic resin may contain no long side chainhydroxyl groups); at least one polyol that contains plural hydroxylgroups in which all the plural hydroxyl groups are connected togetherthrough a chain containing 6 or more carbon atoms (hereafter, simplyreferred to as a “long chain polyol”); and an isocyanate, with apolymerization ratio of 0.1 or more and 10 or less, or about 0.1 or moreand about 10 or less, the polymerization ratio being a ratio (B/A) of atotal molar amount (B) of hydroxyl groups contained in all the polyolsused for the polymerization to a total molar amount (A) of hydroxylgroups contained in all the acrylic resins used for the polymerization.

As described above, a side chain containing 10 or more carbon atoms isdefined as a long side chain; and a side chain containing less than 10carbon atoms is defined as a short side chain. The number of carbonatoms of such a long side chain is preferably 15 or more. The number ofcarbon atoms of such a short side chain is preferably 6 or less. Inparticular, such a long side chain may contain a structure in which anε-lactone ring has been opened, which tends to enhance elasticity.

A resin material formed so as to have the above-described composition bypolymerization has a sufficiently high hardness and a high elasticity.When such a resin material is used for a member for an image formingapparatus, the member being brought into contact with recording mediasuch as paper sheets, the member does not directly bounce in response tothe impact of recording media but flexibly depresses once to reduce theimpact and then recovers from such a depression and goes back to itsoriginal shape due to excellent resilience (that is, self-recoverycapability). Accordingly, extremely high resistance to scratching(resistance to becoming scratched) and quick removal of scratches(removal of scratches having been formed) are probably achieved.

As described above, a resin material according to an exemplaryembodiment is polymerized with a polymerization ratio of 0.1 or more and10 or less or about 0.1 or more and about 10 or less, the polymerizationratio being a ratio (B/A) of the total molar amount (B) of hydroxylgroups contained in all the polyols used for the polymerization to thetotal molar amount (A) of hydroxyl groups contained in all the acrylicresins used for the polymerization. That is, the polymerization isperformed by controlling the polymerization ratio of the polyols to theacrylic resins in accordance with the molar amount of hydroxyl groupscontained in the polyols and the molar amount of hydroxyl groupscontained in the acrylic resins such that the ratio (B/A) falls withinthe above-described range.

Elastic Modulus, Recovery Proportion, and Martens Hardness

A resin material according to an exemplary embodiment may have a highelastic modulus, which results in a high rate of removing scratches.

The elastic modulus may be adjusted by controlling, for example, thestructure or the amount of a polyol added or the type of a cross-linkingagent.

A resin material according to an exemplary embodiment may have a highrecovery proportion in view of resistance to scratching. The recoveryproportion is an indicator of the self-recovery capability (the propertyof recovering from deformation upon removal of a stress, the deformationbeing caused by the stress; that is, the degree of recovery fromscratches) of the resin material.

The recovery proportion may be adjusted by controlling, for example, theamount of long side chain hydroxyl groups, the amount of short sidechain hydroxyl groups, the amount of a long chain polyol, the chainlength of a long chain polyol, or the type of a cross-linking agent.Specifically, the recovery proportion tends to increase by increasingthe amount of long side chain hydroxyl groups and increasing the amountof a long chain polyol. In contrast, the recovery proportion tends todecrease by decreasing the amount of a long chain polyol added.

Although the Martens hardness of a resin material according to anexemplary embodiment depends on an application of the resin material,the resin material preferably has a Martens hardness of 1 N/mm² or moreand 20 N/mm² or less and, in particular, preferably 2 N/mm² or more and10 N/mm² or less.

When a resin material has a Martens hardness of 1 N/mm² or more, theshape of a resin layer composed of the resin material is effectivelymaintained and the resin material is suitably used for a fixing memberor the like. However, a material having a relatively low hardness tendsto readily remove scratches.

The Martens hardness is adjusted by controlling, for example, the amountof long side chain hydroxyl groups, the amount of short side chainhydroxyl groups, the amount of a long chain polyol, the chain length ofa long chain polyol, or the type of a cross-linking agent. Specifically,the Martens hardness tends to increase by decreasing the amount of along chain polyol added. In contrast, the Martens hardness tends todecrease by increasing the amount of long side chain hydroxyl groups.

Measurement Method

A FISCHERSCOPE HM2000 (manufactured by Fischer Instruments K.K.) is usedas a measurement apparatus. A sample resin layer formed by applying aresin to a polyimide film and polymerizing the resin is fixed on a slideglass by using an adhesive agent and placed in the measurementapparatus. The sample resin layer is subjected to an increasing load upto 0.5 mN over 15 seconds at room temperature (23° C.) and the sampleresin layer is held under the load of 0.5 mN for 5 seconds. At thistime, the maximum displacement of the sample resin layer is defined ash1. After that, the load is decreased to 0.005 mN over 15 seconds andthe sample resin layer is held under the load of 0.005 mN for a minute.At this time, the displacement of the sample resin layer is defined ash2. The recovery proportion [(h1−h2)/h1] is then calculated. Inaddition, the Martens hardness and the elastic modulus are determinedfrom a load displacement curve obtained at this time.

Dynamic Contact Angle (Advancing Contact Angle)

A resin material according to an exemplary embodiment preferably has adynamic contact angle (advancing contact angle) of 90° or more and 150°or less, or about 90° or more and about 150° or less, in particular,preferably 110° or more and 150° or less.

When the dynamic contact angle (advancing contact angle) is 90° or moreor about 90° or more, excellent releasability is provided.

The dynamic contact angle is adjusted by controlling the amount offluorine atoms contained in the acrylic resin and the long chain polyol.

Measurement Method

The dynamic contact angle (advancing contact angle) is measured in thefollowing manner. A water droplet is dropped on a solid surface of aresin material by using a syringe. The water droplet is expanded byinjecting water thereinto. A contact angle at an instant when thecontact surface between the resin material and the water increases ismeasured as the dynamic (advancing) contact angle.

Hereinafter, the composition of a resin material according to anexemplary embodiment will be described.

Acrylic Resin

An acrylic resin according to an exemplary embodiment is an acrylicresin that contains hydroxyl groups of side chains each containing lessthan 10 carbon atoms. (short side chain hydroxyl groups) and that doesnot contain hydroxyl groups of side chains each containing 10 or morecarbon atoms (long side chain hydroxyl groups); or an acrylic resin inwhich the content ratio (molar ratio) of long side chain hydroxyl groupsto short side chain hydroxyl groups is less than 1/3.

Examples of a monomer for forming such an acrylic resin will be listedbelow. Examples of a monomer containing a hydroxyl group include (1)ethylenic monomers containing hydroxyl groups such as hydroxymethyl(meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl (meth)acrylate, and N-methylolacrylamine.(2) An ethylenic monomer containing a carboxyl group may be used andexamples thereof include (meth)acrylic acid, crotonic acid, itaconicacid, fumaric acid, and maleic acid. As for a monomer having no hydroxylgroups, (3) an ethylenic monomer that is polymerizable with (1) and (2)may be used with (1) and/or (2) and examples thereof include(meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, n-propyl(meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate,2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, and n-dodecyl(meth)acrylate. When the acrylic resin is made to contain long sidechain hydroxyl groups, a monomer in which 3-5 moles of ε-caprolactone isadded to hydroxymethyl (meth)acrylate may be used. The acrylic resin maybe a single resin or two or more resins.

The acrylic resin does not contain long side chain hydroxyl groups orhas a content ratio (molar ratio) of long side chain hydroxyl groups toshort side chain hydroxyl groups, the content ratio being less than 1/3.

The acrylic resin may contain a fluorine atom. Examples of an acrylicresin containing a fluorine atom include copolymers prepared byperforming the polymerization with an additional monomer such as2-(perfluorobutyl)ethylacrylate, 2-(perfluorohexyl)ethylacrylate,2-(perfluorohexyl)ethylmethacrylate, or perfluorohexylethylene.

The content of such a monomer containing a fluorine atom is preferably0.1 or more and 0.7 or less (molar ratio), more preferably 0.2 or moreand 0.5 or less (molar ratio), relative to the entire monomers used forthe synthesis of the acrylic resin.

Such an acrylic resin according to an exemplary embodiment issynthesized by a method of mixing the above-described monomers,subjecting the mixed monomers to standard radical polymerization, ionicpolymerization, or the like, and then purifying the resultant polymer.

Long Chain Polyol

The long chain polyol that contains plural hydroxyl groups that are allconnected together through a chain containing 6 or more carbon atoms(the number of carbon atoms in a linear chain portion through which thehydroxyl groups are connected together) is not particularly restricted.Examples of such a long chain polyol include bifunctionalpolycaprolactone diols that are compounds represented by the followinggeneral formula (1), trifunctional polycaprolactone triols that arecompounds represented by the following general formula (2), andtetrafunctional polycaprolactone polyols. Such a long chain polyol maybe used alone or in combination of two or more thereof.

In the formula (1), R represents any one of C₂H₄, C₂H₄OC₂H₄, andC(CH₃)₂(CH₂)₂; and m and n independently represent an integer of 4 ormore and 35 or less.

In the formula (2), R represents any one of CH₂CHCH₂, CH₃C(CH₂)₂, andCH₃CH₂C(CH₂)₃; and l+m+n satisfies an integer of 3 or more and 30 orless.

The long chain polyol may contain a fluorine atom. Examples of a longchain polyol containing a fluorine atom include1H,1H,9H,9H-perfluoro-1,9-nonanediol, fluorinated tetraethylene glycol,and 1H,1H,8H,8H-perfluoro-1,8-octanediol.

As for the content of such a long chain polyol containing a fluorineatom, the long chain polyol containing a fluorine atom is added suchthat a ratio (B/A) is 0.1 or more and 10 or less, or about 0.1 or moreand about 10 or less, the ratio (B/A) being a ratio of the total molaramount (B) of hydroxyl groups contained in all the long chain polyols(including long chain polyols containing fluorine atoms and long chainpolyols not containing fluorine atoms) used for the polymerization tothe total molar amount (A) of hydroxyl groups contained in all theacrylic resins used for the polymerization.

The number of functional groups of the long chain polyol is preferably 2to 5, more preferably 2 to 3.

The ratio (B/A) of the total molar amount (B) of hydroxyl groupscontained in all the long chain polyols used for the polymerization tothe total molar amount (A) of hydroxyl groups contained in all theacrylic resins used for the polymerization is 0.1 or more and 10 orless, or about 0.1 or more and about 10 or less. The ratio (B/A) ispreferably 1 or more and 4 or less.

When the ratio is 0.1 or more and 10 or less, or about 0.1 or more andabout 10 or less, high resistance to scratching is provided.

Isocyanate

The isocyanate functions as a cross-linking agent that crosslinks theacrylic resin and the long chain polyol, the acrylic resins, or the longchain polyols. The isocyanate is not particularly restricted. Examplesof the isocyanate include methylene diisocyanate, toluene diisocyanate,hexamethylene diisocyanate, and isophorone diisocyanate. As for such anisocyanate, a single isocyanate or two or more isocyanates may be used.

As for the content of the isocyanate, the number of moles of isocyanategroups may be 0.5 times or more and 3 times or less the total number ofmoles of hydroxyl groups of the acrylic resin and the polyol.

Polymerization Method

Hereinafter, a method for forming a resin material according to anexemplary embodiment (a method for polymerizing a resin) will bedescribed. A method for forming a sample is as follows. An acrylicresin, a long chain polyol, and an isocyanate are mixed together. Theresultant mixture is subjected to defoaming under a reduced pressure andthen cast onto a polyimide film having a thickness of 90 μm to form aresin layer sample for evaluation. The resin layer sample is heated at85° C. for 60 minutes and at 130° C. for 0.5 hours to be cured.Practically, the mixture is applied to a surface that is to be protectedand then heated in a similar manner to be cured.

The thus-obtained resin material according to an exemplary embodiment isused for a surface protective layer for an endless belt or a roller inan image forming apparatus. In particular, such a resin material issuitably used for a fixing belt or a fixing roller of a fixing device,an intermediate transfer belt or an intermediate transfer roller of anintermediate transfer device, a recording medium transport belt, arecording medium transport roller, a frame surface, or the like.

Hereinafter, a member for an image forming apparatus including a resinmaterial according to an exemplary embodiment will be described.

Endless Belt

FIG. 1 is a perspective (partially cutaway) view of an endless beltaccording to an exemplary embodiment. FIG. 2 is a sectional view of theendless belt viewed in the direction of arrow II in FIG. 1.

As illustrated in FIGS. 1 and 2, an endless belt 1 according to anexemplary embodiment is an endless belt including a base member 2 and asurface layer 3 stacked on a surface of the base member 2.

For the surface layer 3, the above-described resin material according toan exemplary embodiment is used.

An application of the endless belt 1 is, for example, a fixing belt, anintermediate transfer belt, or a recording medium transport belt in animage forming apparatus.

Hereinafter, a case where the endless belt 1 is used as a fixing beltwill be described.

A material used for the base member 2 may be a heat resistant material.Specifically, such a material may be selected from existing variousplastic materials and metal materials.

Among plastic materials, those generally referred to as engineeringplastics are suitably used. Preferred examples of such engineeringplastics include fluorocarbon resins, polyimide (PI), polyamide imide(PAI), polybenzimidazole (PBI), polyether ether ketone (PEEK),polysulfone (PSU), polyether sulfone (PES), polyphenylene sulfide (PPS),polyether imide (PEI), and wholly aromatic polyesters (liquid crystalpolymers). Of these, those that are excellent in terms of mechanicalstrength, heat resistance, wear resistance, chemical resistance, and thelike such as thermosetting polyimide, thermoplastic polyimide, polyamideimide, polyether imide, and fluorocarbon resins are preferred.

A metal material used for the base member 2 is not particularlyrestricted. Various metals and alloy materials may be used. For example,SUS, nickel, copper, aluminum, iron, or the like is suitably used. Sucha heat resistant resin and such a metal material may be stacked to forma multilayer structure.

Hereinafter, a case where the endless belt 1 is used as an intermediatetransfer belt or a recording medium transport belt will be described.

Examples of a material used for the base member 2 may be polyimideresins, polyamide imide resins, polyester resins, polyamide resins, andfluorocarbon resins. Of these, use of a polyimide resin and a polyamideimide resin is preferred. The base member 2 may include a joint or notas long as the base member 2 is annular (endless). The base member 2 maygenerally have a thickness of 0.02 to 0.2 mm.

When the endless belt 1 is used as an intermediate transfer belt or arecording medium transport belt of an image forming apparatus, thesurface resistivity of the endless belt 1 may be controlled within therange of 1×10⁹ to 1×10¹⁴ ohms per square and the volume resistivity ofthe endless belt 1 may be controlled within the range of 1×10⁸ to 1×10¹³Ωcm. To achieve such conditions, if necessary, a conductive agent may beadded to the base member 2 and/or the surface layer 3 as describedabove. An example of such a conductive agent is carbon black such asKetjenblack or acetylene black; graphite; a metal or an alloy such asaluminum, nickel, or a copper alloy; a metal oxide such as tin oxide,zinc oxide, potassium titanate, a composite oxide of tin oxide-indiumoxide, or a composite oxide of tin oxide-antimony oxide; or a conductivepolymer such as polyaniline, polypyrrole, polysulfone, or polyacethylene(here, the term “conductive” of the polymer refers to having a volumeresistivity of less than 10⁷ Ωcm). Such a conductive agent may be usedalone or in combination of two or more thereof.

The surface resistivity and the volume resistivity are measured with aUR probe of a Hiresta UPMCP-450 manufactured by DIA Instruments Co.,Ltd. in an environment at 22° C. and 55% RH in compliance withJIS-K6911.

In the cases of fixing applications, the endless belt 1 may include anelastic layer between the base member 2 and the surface layer 3.Examples of a material of such an elastic layer include various rubbermaterials. Examples of such various rubber materials includepolyurethane rubbers, ethylene propylene rubbers (EPM), siliconerubbers, and fluoro rubbers (EKM). In particular, silicone rubbers,which are excellent in terms of heat resistance and processibility, arepreferred. Examples of such silicone rubbers include room temperaturevulcanization (RTV) silicone rubbers and high temperature vulcanization(HTV) silicone rubbers. Specific examples of such silicone rubbersinclude polydimethyl silicone rubber (MQ), methyl vinyl silicone rubber(VMQ), methyl phenyl silicone rubber (PMQ), and fluoro silicone rubber(FVMQ).

When the endless belt 1 is used as a fixing belt in an electromagneticinduction fixing device, a heating layer may be disposed between thebase member 2 and the surface layer 3.

A material used for the heating layer is, for example, a nonmagneticmetal. Specific examples of such a nonmagnetic metal include metalmaterials such as gold, silver, copper, aluminum, zinc, tin, lead,bismuth, beryllium, antimony, and alloys of the foregoing metals (alloyscontaining the foregoing metals).

The heating layer preferably has a thickness within the range of 5 to 20μm, more preferably within the range of 7 to 15 μm, and, in particular,preferably within the range of 8 to 12 μm.

Roller

Hereinafter, a roller according to an exemplary embodiment will bedescribed. A roller according to an exemplary embodiment is asubstantially tubular roller including a base member and a surface layerstacked on a surface of the base member.

For the surface layer, the above-described resin material according toan exemplary embodiment is used.

An application of such a tubular roller is, for example, a fixingroller, an intermediate transfer roller, or a recording medium transportroller in an image forming apparatus.

Hereinafter, a case where such a tubular roller is used as a fixingroller will be described.

A fixing roller 610 illustrated in FIG. 4 and serving as a fixing memberis not particularly restricted in terms of shape, structure, size, orthe like. The fixing roller 610 includes a tubular core 611 and asurface layer 613 on the tubular core 611. As illustrated in FIG. 4, anelastic layer 612 may be disposed between the core 611 and the surfacelayer 613.

A material of the tubular core 611 is, for example, a metal such asaluminum (e.g. A-5052 member), SUS, iron, or copper, an alloy, aceramic, or a fiber reinforced metal (FRM). The tubular core 611 in afixing device 72 according to an exemplary embodiment is constituted bya tubular member having an outer diameter of 25 mm, a wall thickness of0.5 mm, and a length of 360 mm.

A material of the elastic layer 612 may be selected from existingmaterials and any elastic body having high heat resistance may be used.In particular, an elastic body of, for example, a rubber or an elastomerhaving a rubber hardness of about 15° to 45° (JIS-A) is preferably used.Examples of such an elastic body include silicone rubbers and fluororubbers.

In an exemplary embodiment, of these materials, silicone rubbers arepreferred in view of small surface tension and excellent elasticity.Examples of such silicone rubbers include RTV silicone rubbers and HTVsilicone rubbers. Specific examples of such silicone rubbers includepolydimethyl silicone rubber (MQ), methyl vinyl silicone rubber (VMQ),methyl phenyl silicone rubber (PMQ), and fluoro silicone rubber (FVMQ).

The elastic layer 612 preferably has a thickness of 3 mm or less, morepreferably, a thickness within the range of 0.5 to 1.5 mm. In the fixingdevice 72 according to a first exemplary embodiment, a core is coveredwith a 72 μm-thick layer composed of a HTV silicone rubber having arubber hardness of 35° (JIS-A).

The surface layer 613 preferably has a thickness of 5 to 50 μm, morepreferably 10 to 30 μm.

As for a heating source for heating the fixing roller 610, as describedabove, for example, a halogen lamp 660 is used. As long as the heatingsource has a shape and a structure such that the heating source isinstalled inside the core 611, the heating source is not particularlyrestricted and is selected in accordance with a purpose. The surfacetemperature of the fixing roller 610 heated with the halogen lamp 660 ismeasured with a thereto-sensitive device 690 provided for the fixingroller 610 and the surface temperature is controlled to be constant by acontroller. The thermo-sensitive device 690 is not particularlyrestricted and may be a thermistor, temperature sensor, or the like.

Image Forming Apparatus and Image Fixing Device First ExemplaryEmbodiment

Hereinafter, an image forming apparatus according to a first exemplaryembodiment including an endless belt according to an exemplaryembodiment and a roller according to an exemplary embodiment will bedescribed. FIG. 3 is a schematic view for illustrating a portion of atandem-system image forming apparatus including an endless beltaccording to an exemplary embodiment serving as a pressure belt of afixing device, an endless belt according to an exemplary embodimentserving as an intermediate transfer belt, and a roller according to anexemplary embodiment serving as a fixing roller of the fixing device.

Specifically, an image forming apparatus 101 includes a photoconductorbody 79 (electrostatic latent image holding body), a charging roller 83for charging the surface of the photoconductor body 79, a lasergenerating device 78 (electrostatic latent image forming part) forforming an electrostatic latent image by exposing the surface of thephotoconductor body 79, a developing device 85 (developing part) fordeveloping the latent image formed on the surface of the photoconductorbody 79 by using a developer to form a toner image, an intermediatetransfer belt 86 (intermediate transfer body) onto which the toner imageformed by the developing device 85 is transferred from thephotoconductor body 79, a first transfer roller 80 (first transfer part)for transferring the toner image onto the intermediate transfer belt 86,a photoconductor-body cleaning member 84 for removing toner, foreignparticles, and the like adhering to the photoconductor body 79, a secondtransfer roller 75 (second transfer part) for transferring the tonerimage on the intermediate transfer belt 86 onto a recording medium, andthe fixing device 72 (fixing part) for fixing the toner image on therecording medium. As illustrated in FIG. 3, the first transfer roller 80may be disposed immediately above the photoconductor body 79.Alternatively, the first transfer roller 80 may be disposed at aposition displaced with respect to the position immediately above thephotoconductor body 79.

The configuration of the image forming apparatus 101 illustrated in FIG.3 will be described further in detail.

In the image forming apparatus 101, the charging roller 83, thedeveloping device 85, the first transfer roller 80 disposed beyond theintermediate transfer belt 86, and the photoconductor-body cleaningmember 84 are disposed counterclockwise around the photoconductor body79. Such members constitute a developing unit corresponding to a singlecolor. A toner cartridge 71 for supplying a developer to the developingdevice 85 is provided for each developing unit. The laser generatingdevice 78 is disposed for the photoconductor bodies 79 of the developingunits. The laser generating device 78 irradiates a surface portion ofeach photoconductor body 79 with laser light in accordance with imageinformation, the surface portion being downstream of the charging roller83 (in the direction in which the photoconductor body 79 is rotated) andupstream of the developing device 85.

Four developing units corresponding to four colors (for example, cyan,magenta, yellow, and black) are horizontally arranged in a line in theimage forming apparatus 101. The intermediate transfer belt 86 isdisposed so as to be passed through transfer regions between thephotoconductor bodies 79 and the first transfer rollers 80 of the fourdeveloping units. The intermediate transfer belt 86 is supported so asto be stretched by a support roller 73, a support roller 74, and adriving roller 81 that are sequentially disposed counterclockwise insidethe intermediate transfer belt 86. Thus, a belt stretching device 90 isprovided. The four first transfer rollers 80 are disposed downstream ofthe support roller 73 (in the direction in which the intermediatetransfer belt 86 is rotated) and upstream of the support roller 74. Atransfer cleaning member 82 for cleaning the outer peripheral surface ofthe intermediate transfer belt 86 is disposed opposite the drivingroller 81 through the intermediate transfer belt 86 so as to be incontact with the driving roller 81.

The second transfer roller 75 for transferring a toner image formed onthe outer peripheral surface of the intermediate transfer belt 86 onto asurface of a recording paper sheet transported from a paper sheetsupplying section 77 through a paper sheet path 76 is disposed oppositethe support roller 73 through the intermediate transfer belt 86 so as tobe in contact with the support roller 73.

The paper sheet supplying section 77 that contains recording media isprovided in a bottom portion of the image forming apparatus 101. Arecording medium is supplied from the paper sheet supplying section 77so as to be passed through the paper sheet path 76 and the nip betweenthe support roller 73 and the second transfer roller 75 that constitutea second transfer unit. The recording medium having been passed throughthe nip is further transported by a transport part (not shown) so as tobe passed through the nip of the fixing device 72. Finally, therecording medium is discharged from the image forming apparatus 101.

Hereinafter, a method for forming an image by using the image formingapparatus 101 illustrated in FIG. 3 will be described. The formation ofa toner image is performed in each developing unit. The surface of thephotoconductor body 79 being rotated counterclockwise is charged withthe charging roller 83. Then, a latent image (electrostatic latentimage) is formed on the charged surface of the photoconductor body 79 byusing the laser generating device 78 (exposure device). Then, the latentimage is developed with a developer supplied from the developing device85 to form a toner image. The toner image having been transported to thenip between the first transfer roller 80 and the photoconductor body 79is transferred onto the outer peripheral surface of the intermediatetransfer belt 86 being rotated in the direction represented by arrow C.The photoconductor body 79 after the transfer of a toner image issubjected to cleaning of toner, foreign particles, and the like adheringto the surface of the photoconductor body 79 by using thephotoconductor-body cleaning member 84. Thus, the photoconductor body 79is prepared for the next formation of a toner image.

The toner images developed by the developing units corresponding tocolors are sequentially stacked on the outer peripheral surface of theintermediate transfer belt 86 so as to correspond to image information.The thus-stacked toner images are transported to a second transfer unitand transferred by the second transfer roller 75 onto a surface of arecording paper sheet having been transported from the paper sheetsupplying section 77 through the paper sheet path 76. The recordingpaper sheet onto which the toner images have been transferred is thenpressed and heated when the recording paper sheet is passed through thenip of the fixing device 72. As a result, the toner images are fixed toform an image on the surface of the recording medium. Then, therecording medium is discharged from the image forming apparatus.

Fixing Device (Image Fixing Device)

FIG. 4 is a schematic view of the configuration of the fixing device 72installed in the image forming apparatus 101 according to an exemplaryembodiment. The fixing device 72 illustrated in FIG. 4 includes thefixing roller 610 serving as a rotational body that is driven so as torotate, an endless belt 620 (pressure belt), and a pressure pad 640serving as a pressing member configured to press the fixing roller 610through the endless belt 620. It will suffice that the pressure pad 640press the endless belt 620 and the fixing roller 610 toward each other.Accordingly, the endless belt 620 may be pressed by the fixing roller610 or the fixing roller 610 may be pressed by the endless belt 620.

The halogen lamp 660 serving as an example of a heating part for heatingunfixed toner images in a nipping region is disposed inside the fixingroller 610. The heating part is not restricted to a halogen lamp andanother heating member generating heat may be used.

The thermo-sensitive device 690 is disposed on the surface of the fixingroller 610 so as to be in contact with the fixing roller 610. Turning onof the halogen lamp 660 is controlled on the basis of temperature valuesmeasured with the thereto-sensitive device 690 to maintain the surfacetemperature of the fixing roller 610 to be a specified temperature (forexample, 150° C.)

The endless belt 620 is rotatably supported by the pressure pad 640, abelt running guide 630, and an edge guide (not shown), the pressure pad640 and the belt running guide 630 being disposed inside the endlessbelt 620. In a nipping region N, the endless belt 620 is disposed underpressure so as to be in contact with the fixing roller 610.

The pressure pad 640 is disposed inside the endless belt 620 so as topress the fixing roller 610 through the endless belt 620. Thus, thepressure pad 640 and the fixing roller 610 form the nipping region Ntherebetween. In the pressure pad 640, a pre-nipping member 641 forproviding a wide nipping region N is disposed on the entrance side ofthe nipping region N and a peeling nipping member 642 for distorting thefixing roller 610 is disposed on the exit side of the nipping region N.

To decrease the sliding resistance between the inner circumferentialsurface of the endless belt 620 and the pressure pad 640, a low-frictionsheet 680 is disposed on the surfaces of the pre-nipping member 641 andthe peeling nipping member 642, the surfaces being in contact with theendless belt 620. The pressure pad 640 and the low-friction sheet 680are held by a metal holder 650.

The holder 650 is equipped with the belt running guide 630 so that theendless belt 620 is rotated smoothly. Specifically, since the innercircumferential surface of the endless belt 620 slides against the beltrunning guide 630, the belt running guide 630 is composed of a materialhaving a low coefficient of static friction. In addition, the materialof the belt running guide 630 has a low thermal conductivity such thatthe belt running guide 630 is less likely to deprive the endless belt620 of heat.

The fixing roller 610 is rotated in the direction represented by arrow Cby a driving motor (not shown). Such rotation drives the endless belt620 in a direction opposite to the direction in which the fixing roller610 is rotated. That is, the fixing roller 610 is rotated clockwise inFIG. 4, whereas the endless belt 620 is rotated counterclockwise.

A paper sheet K including unfixed toner images is guided by a fixingentrance guide 560 and transported to the nipping region N. When thepaper sheet K is then passed through the nipping region N, the tonerimages on the paper sheet K are fixed by pressure applied to the nippingregion N and heat supplied by the fixing roller 610.

In the fixing device 72, the pre-nipping member 641 having a recessconforming to the outer circumferential surface of the fixing roller 610provides the nipping region N.

In the fixing device 72 according to an exemplary embodiment, bydisposing the peeling nipping member 642 so as to project toward theouter circumferential surface of the fixing roller 610, the distortionof the fixing roller 610 is locally made large in the exit region of thenipping region N. In such a configuration, after fixing, the paper sheetK is peeled from the fixing roller 610.

A peeling member 700 serving as a peeling auxiliary part is disposeddownstream of the nipping region N, for the fixing roller 610. In thepeeling member 700, a peeling baffle 710 is held in a direction (counterdirection) intersecting the direction in which the fixing roller 610 isrotated, by a holder 720 so as to be in close proximity to the fixingroller 610.

Hereinafter, members other than the endless belt 620 and the fixingroller 610 in the fixing device 72 according to an exemplary embodimentwill be described in detail.

As described above, the pressure pad 640 disposed inside the endlessbelt 620 includes the pre-nipping member 641 and the peeling nippingmember 642. The pressure pad 640 is supported by the holder 650 suchthat a spring or an elastic body presses the fixing roller 610 with aload of, for example, 32 kgf. A surface of the pressure pad 640, thesurface facing the fixing roller 610, is formed so as to have a recessedcurve conforming to the outer circumferential surface of the fixingroller 610. The pre-nipping member 641 and the peeling nipping member642 may be composed of a material having heat resistance.

The shape and the material of the pressure pad 640 disposed inside theendless belt 620 are not particularly restricted as long as the pressurepad 640 functions to press the fixing roller 610 through the endlessbelt 620 and to form the nipping region N through which a paper sheet Kincluding an unfixed toner image is passed between the endless belt 620and the fixing roller 610. In addition to the pressure pad 640, forexample, a pressure roller configured to press the fixing roller 610while being rotated may also be disposed.

As for the pre-nipping member 641, a heat resistant elastomer such as asilicone rubber or a fluoro rubber or an elastic body such as a leafspring is used. Of such materials, silicone rubber is preferred in viewof excellent elasticity. Examples of such a silicone rubber include RTVsilicone rubbers and HTV silicone rubbers. Specific examples of suchsilicone rubbers include polydimethyl silicone rubber (MQ), methyl vinylsilicone rubber (VMQ), methyl phenyl silicone rubber (PMQ), and fluorosilicone rubber (FVMQ). A silicone rubber having a JIS-A hardness of 10°to 40° is preferably used in view of hardness. The shape, structure,size, and the like of such an elastic body are not particularlyrestricted and are selected in accordance with a purpose. In the fixingdevice 72 according to an exemplary embodiment, a silicone rubber memberhaving a width of 10 mm, a thickness of 5 mm, and a length of 320 mm isused.

The peeling nipping member 642 is composed of a heat resistant resinsuch as PPS (polyphenylene sulfide), polyimide, polyester, or polyamide;or a metal such as iron, aluminum, or SUS. As for the shape of thepeeling nipping member 642, the peeling nipping member 642 is formed soas to have an outer shape in the nipping region N, the outer shape beinga convex curved surface having a certain radius of curvature. In thefixing device 72 according to an exemplary embodiment, the endless belt620 is wrapped around the fixing roller 610 at a wrapping angle of 40°by using the pressure pad to form the nipping region N having a width of8 mm.

The low-friction sheet 680 is disposed in order to decrease the slidingresistance (frictional resistance) between the inner circumferentialsurface of the endless belt 620 and the pressure pad 640. For thelow-friction sheet 680, a material having a low coefficient of frictionand being excellent in terms of wear resistance and heat resistance issuitably used.

Examples of a material for the low-friction sheet 680 include variousmaterials such as metals, ceramics, and resins. Specific examples ofsuch materials include heat resistant resins such as fluorocarbonresins, polyether sulfone (PES), polybutylene terephthalate (PET),liquid crystal polymers (LOP), polyphenylene sulfide (PPS), andpolyethylene terephthalate (PET); natural materials of 6-nylon andnatural materials of 6,6-nylon; and materials in which carbon, glassfiber, or the like is added to the foregoing materials.

In particular, a fluorocarbon resin sheet in which a surface being incontact with the endless belt 620 has a low sliding resistance againstthe inner circumferential surface of the endless belt 620 and a surfaceon which lubricant is held has micro-irregularities is preferred.

Specifically, for example, a PTFE resin sheet formed by sintering, aglass fiber sheet impregnated with Teflon (registered trademark), alaminate sheet in which a skived film sheet composed of a fluorocarbonresin is sandwiched by heat sealing between glass fiber sheets, or afluorocarbon resin sheet in which streak-shaped irregularities areformed is used.

The low-friction sheet 680 may be formed as an independent memberseparate from the pre-nipping member 641 and the peeling nipping member642. Alternatively, the low-friction sheet 680 may be integrally formedtogether with the pre-nipping member 641 and the peeling nipping member642.

A lubricant applying member 670 is also disposed in the holder 650 so asto extend in the longitudinal direction of the fixing device 72. Thelubricant applying member 670 is disposed so as to be in contact withthe inner circumferential surface of the endless belt 620 and suppliesan appropriate amount of a lubricant to the endless belt 620. Thus, thelubricant is supplied to the portion where the endless belt 620 slidesagainst the low-friction sheet 680 and the sliding resistance betweenthe endless belt 620 and the pressure pad 640 through the low-frictionsheet 680 is further decreased. In this way, smooth rotation of theendless belt 620 is achieved. The lubricant applying member 670 alsoprovides an effect of suppressing wear of the inner circumferentialsurface of the endless belt 620 and the surface of the low-frictionsheet 680.

Such a lubricant may be a silicone oil. An example of such a siliconeoil is a dimethyl silicone oil, an organometallic-salt-added dimethylsilicone oil, a hindered-amine-added dimethyl silicone oil, anorganometallic-salt-and-hindered-amine-added dimethyl silicone oil, amethylphenyl silicone oil, an amino-modified silicone oil, anorganometallic-salt-added amino-modified silicone oil, ahindered-amine-added amino-modified silicone oil, a carboxy-modifiedsilicone oil, a silanol-modified silicone oil, a sulfonic-acid-modifiedsilicone oil, or the like. Of these, an amino-modified silicone oil,which has excellent wettability, is preferably used.

In the image fixing device 72 according to an exemplary embodiment, thelubricant applying member 670 is used to supply a lubricant to the innercircumferential surface of the endless belt 620. Alternatively, aconfiguration in which a lubricant applying member and a lubricant arenot used may be employed.

A methylphenyl silicone oil, a fluorocarbon oil (a perfluoropolyetheroil or a modified perfluoropolyether oil), or the like is suitably used.An anti-oxidizing agent may be added to a silicone oil. A syntheticlubricant oil grease in which a solid substance and a liquid are mixedtogether such as a silicone grease, a fluorocarbon grease, or acombination of such greases may be used. In the fixing device 72according to an exemplary embodiment, an amino-modified silicone oilhaving a viscosity of 300 cs (KF96 manufactured by Shin-Etsu ChemicalCo., Ltd.) is used.

As described above, the inner circumferential surface of the endlessbelt 620 slides against the belt running guide 630. Thus, the beltrunning guide 630 may be composed of a material having a low coefficientof friction and a low thermal conductivity such that the belt runningguide 630 is less likely to deprive the endless belt 620 of heat.Accordingly, a heat resistant resin such as PFA or PPS is used.

In the image forming apparatus 101 according to an exemplary embodiment,an endless belt according to the above-described exemplary embodiment isused as the endless belt 620 of the fixing device 72. However, anendless belt according to the above-described exemplary embodiment maybe used as the intermediate transfer belt 86.

Second Exemplary Embodiment

An image forming apparatus according to a second exemplary embodimenthas a configuration in which, instead of the fixing device 72 disposedin the image forming apparatus 101 according to the first exemplaryembodiment, a fixing device including a fixing belt including a heatingsource (the fixing belt being an endless belt according to an exemplaryembodiment) and a pressure roller (a roller according to an exemplaryembodiment) is used. Since the second exemplary embodiment is the sameas the first exemplary embodiment except that the different fixingdevice is used, descriptions of the common features are omitted.

Fixing Device (Image Fixing Device)

FIG. 5 is a schematic view of the configuration of a fixing deviceaccording to the second exemplary embodiment. Specifically, FIG. 5illustrates a fixing device including an endless belt according to anexemplary embodiment serving as a fixing belt and a roller according toan exemplary embodiment serving as a pressure roller. Components similarto those in the fixing device according to the first exemplaryembodiment are denoted with the same reference numerals and detaileddescriptions of such components are omitted.

As illustrated in FIG. 5, a fixing device 900 according to the secondexemplary embodiment includes a fixing belt 920, which is an endlessbelt, and a pressure roller 910 serving as an example of a rotationalbody that is driven so as to rotate. The fixing belt 920 has the sameconfiguration as the above-described endless belt 620.

The fixing belt 920 is disposed so as to face a surface of the papersheet K, the surface holding a toner image. A ceramic heater 820 that isa heating resistor serving as an example of a heating part is disposedinside the fixing belt 920. The ceramic heater 820 is configured tosupply heat to the nipping region N.

As for the ceramic heater 820, a surface facing the pressure roller 910is formed so as to be flat. The ceramic heater 820 is disposed so as topress the pressure roller 910 through the fixing belt 920 to form thenipping region N. Thus, the ceramic heater 820 also functions as apressing member. The paper sheet K having been passed through thenipping region N is peeled from the fixing belt 920 in the exit region(peeling nipping region) of the nipping region N due to change in thecurvature of the fixing belt 920.

To decrease the sliding resistance between the inner circumferentialsurface of the fixing belt 920 and the ceramic heater 820, alow-friction sheet 680 is disposed between the inner circumferentialsurface of the fixing belt 920 and the ceramic heater 820. Thelow-friction sheet 680 may be formed as an independent member separatefrom the ceramic heater 820. Alternatively, the low-friction sheet 680may be integrally formed together with the ceramic heater 820.

The pressure roller 910 is disposed so as to face the fixing belt 920.The pressure roller 910 is rotated in the direction represented by arrowD by a driving motor (not shown). Such rotation causes the fixing belt920 to rotate. The pressure roller 910 includes a stack of a core(cylindrical metal member) 911, a heat-resistant elastic layer 912covering the outer circumferential surface of the core 911, and arelease layer 913 that is a heat-resistant resin coating or aheat-resistant rubber coating. If necessary, each layer is madesemiconductive by addition of carbon black or the like thereto toaddress offsetting of toner.

The peeling member 700 serving as a peeling auxiliary part may bedisposed downstream of the nipping region N, for the fixing belt 920. Inthe peeling member 700, the peeling baffle 710 is held in a direction(counter direction) intersecting the direction in which the fixing belt920 is rotated, by the holder 720 so as to be in close proximity to thefixing belt 920.

The paper sheet K including unfixed toner images is guided by the fixingentrance guide 560 and transported to the nipping region N of the fixingdevice 900. When the paper sheet K is passed through the nipping regionN, the toner images on the paper sheet K are fixed by pressure appliedto the nipping region N and heat supplied by the ceramic heater 820disposed on the fixing belt 920 side of the fixing device 900.

Here, in the fixing device 900 according to an exemplary embodiment, thepressure roller 910 is formed so as to have a reverse crown shape(flaring shape) in which the outer diameters of the two end portions arelarger than the outer diameter of the central portion. The fixing belt920 has an irregularly shaped structure in the inner surface. Thisirregularly shaped structure is configured to deform in the nippingregion so as to expand in conformity to the surface shape of thepressure roller 910. In such a configuration, when a paper sheet ispassed through the nipping region, a tensile force is applied by thepressure roller 910 in the width direction from the central portion tothe two end portions of the paper sheet. Thus, the paper sheet isstretched and the length of the fixing belt 920 in the surface widthdirection is increased.

Accordingly, in the fixing device 900 according to an exemplaryembodiment, slipping of the fixing belt 920 against the paper sheet K issuppressed in the entire region from the central portion to the two endportions of the fixing belt 920.

As for the heating source, other than the ceramic heater 820, a halogenlamp disposed inside the fixing belt 920 or an electromagnetic inductioncoil that is disposed inside or outside of the fixing belt 920 andgenerates heat by electromagnetic induction may be used.

In addition to the flat pressure member, for example, a pressure rollerconfigured to press the pressure roller 910 while being rotated may alsobe disposed inside the fixing belt 920.

Third Exemplary Embodiment

Hereinafter, an image forming apparatus according to a third exemplaryembodiment including an endless belt according to an exemplaryembodiment serving as a paper-sheet transport belt will be described.

FIG. 6 is a schematic view illustrating an image forming apparatusaccording to the third exemplary embodiment. In the image formingapparatus illustrated in FIG. 6, units Y, M, C, and BK respectivelyinclude photoconductor drums 201Y, 201M, 201C, and 201BK that areconfigured to rotate in the clockwise directions indicated by arrows. Inthe proximity of the photoconductor drums 201Y, 201M, 201C, and 201BK,charging devices 202Y, 202M, 202C, and 202BK, exposing devices 203Y,203M, 203C, and 203BK, developing devices corresponding to colors(yellow developing device 204Y, magenta developing device 204M, cyandeveloping device 2040, and black developing device 204BK), andphotoconductor-drum cleaning members 205Y, 205M, 205C, and 205BK arerespectively disposed.

The units Y, M, C, and BK are arranged in parallel with a paper-sheettransport belt 206 in the sequence of the units BK, C, M, and Y.However, for example, the sequence of the units BK, Y, C, and M may beset to an appropriate sequence in accordance with an image formingmethod.

The paper-sheet transport belt 206 is supported so as to be stretched bybelt support rollers 210, 211, 212, and 213 disposed inside thepaper-sheet transport belt 206. Thus, a belt stretching device 220 forthe image forming apparatus is provided. The paper-sheet transport belt206 is configured to be rotated in a counterclockwise directionindicated by arrow at the same peripheral velocity as that of thephotoconductor drums 201Y, 201M, 201C, and 201BK. The paper-sheettransport belt 206 is disposed such that a portion of the paper-sheettransport belt 206, the portion being between the belt support rollers212 and 213, is in contact with the photoconductor drums 201Y, 201M,201C, and 201BK. A belt cleaning member 214 is provided for thepaper-sheet transport belt 206.

Transfer rollers 207Y, 207M, 207C, and 207BK are respectively disposedinside the paper-sheet transport belt 206 and at positions so as to facepositions where the paper-sheet transport belt 206 and thephotoconductor drums 201Y, 201M, 201C, and 201BK are in contact witheach other. Thus, the transfer rollers 207Y, 207M, 207C, and 207BK, thephotoconductor drums 201Y, 201M, 201C, and 201BK, and the paper-sheettransport belt 206 form transfer regions where toner images aretransferred onto a paper sheet (receiver) 216. As illustrated in FIG. 6,the transfer rollers 207Y, 207M, 207C, and 207BK may be respectivelydisposed immediately below the photoconductor drums 201Y, 201M, 201C,and 201BK. Alternatively, the transfer rollers 207Y, 207M, 207C, and207BK may be respectively disposed at positions displaced with respectto the positions immediately below the photoconductor drums 201Y, 201M,201C, and 201BK.

A fixing device 209 is disposed such that the paper sheet is transportedto the fixing device 209 after the paper sheet is passed through thetransfer regions formed between the paper-sheet transport belt 206 andthe photoconductor drums 201Y, 201M, 201C, and 201BK.

The paper sheet 216 is transported to the paper-sheet transport belt 206by a paper-sheet transport roller 208.

In the image forming apparatus according to the third exemplaryembodiment illustrated in FIG. 6, in the unit BK, the photoconductordrum 201BK is driven so as to be rotated. Such rotation operativelydrives the charging device 202BK and the charging device 202BK chargesthe surface of the photoconductor drum 201BK such that the surface hasan intended polarity and potential. The photoconductor drum 201BK whosesurface is thus charged is then subjected to image exposure by using theexposing device 203BK. Thus, an electrostatic latent image is formed onthe surface of the photoconductor drum 201BK.

Then, the electrostatic latent image is developed with the blackdeveloping device 204BK. Thus, a toner image is formed on the surface ofthe photoconductor drum 201BK. A developer used at this time may be asingle component developer or a two component developer.

The thus-formed toner image is passed through the transfer region formedbetween the photoconductor drum 201BK and the paper-sheet transport belt206. The paper sheet 216 is electrostatically attracted to thepaper-sheet transport belt 206 and transported to the transfer region.The toner image is sequentially transferred onto a surface of the papersheet 216 by an electric field formed by a transfer bias applied fromthe transfer roller 207BK.

After that, toner remaining on the photoconductor drum 201BK is cleanedand removed by the photoconductor-drum cleaning member 205BK. Thus, thephotoconductor drum 201BK is prepared for the next image transfer.

The above-described image transfer is also performed in the units C, M,and Y in the above-described manner.

The paper sheet 216 onto which toner images have been transferred by thetransfer rollers 207BK, 207C, 207M, and 207Y is then transported to thefixing device 209 and the toner images are fixed on the paper sheet 216.

As a result, an intended image is formed on the paper sheet.

EXAMPLES

Hereinafter, exemplary embodiments according to the present inventionwill be described in detail with reference to examples. However, thepresent invention is not restricted to the examples described below. Inthe following description, “parts” and “%” are based on mass unlessotherwise specified.

Sample Preparation Method Example 1 Synthesis of Acrylic ResinPrepolymer A1

A monomer solution composed of 286.8 parts of hydroxyethyl methacrylate(HEMA, the number of carbon atoms in a side chain containing a hydroxylgroup: 3) serving as monomers providing short side chain hydroxylgroups, 313.2 parts of butyl methacrylate (BMA), 27 parts of apolymerization initiator (benzoyl peroxide, BPO), and 60 parts of butylacetate was charged into a dropping funnel and dropped into 300 parts ofbutyl acetate that was heated to 110° C. and being stirred over threehours under nitrogen flow to polymerize the monomers. Furthermore, asolution composed of 135 parts of butyl acetate and 3 parts of BPO wasdropped to this reaction solution over an hour to complete the reaction.The reaction solution was always maintained at 110° C. and being stirredduring the reaction. As a result, an acrylic resin prepolymer A1 notcontaining long side chain hydroxyl groups was synthesized.

Formation of Resin Layer Sample A1

The following solutions A and B were mixed together in the followingproportions and the following solution C was further added thereto. Theresultant mixture was defoamed for 10 minutes under a reduced pressure.The thus-prepared solution was cast onto a polyimide film having athickness of 90 μm and cured at 85° C. for an hour and at 130° C. for 30minutes. Thus, a resin layer sample A1 having a thickness of 40 μm wasobtained.

Solution A (solution of the above-described acrylic resin prepolymer A1,44.2%, hydroxyl value: 206): 113 parts

Solution B (polyol, manufactured by DAICEL CHEMICAL INDUSTRIES, LTD.,PLACCEL 208, polycaprolactonediol, hydroxyl value: 138, hydroxyl groupsare connected to each other through a chain containing about 42 carbonatoms): 149.6 parts

Solution C (isocyanate, manufactured by Asahi Kasei ChemicalsCorporation, Duranate TKA100, compound name: hexamethylenediisocyanate-based polyisocyanurate): 138.2 parts

The total molar amount (A) of the hydroxyl groups of the acrylic resinprepolymer in the solution A was 0.184 mol. The total molar amount (B)of the hydroxyl groups of the polyol in the solution B was 0.37 mol.Thus, the ratio (B/A) was 2.

Example 2

A resin layer sample A2 was obtained in the same manner as in Example 1except that the amount of the solution B was changed to 14.96 parts andthe amount of the solution C was changed to 55.28 parts in “Formation ofresin layer sample A1” in Example 1. The total molar amount (A) of thehydroxyl groups of the acrylic resin prepolymer in the solution A was0.184 mol. The total molar amount (B) of the hydroxyl groups of thepolyol in the solution B was 0.037 mol. Thus, the ratio (B/A) was 0.2.

Example 3

A resin layer sample A3 was obtained in the same manner as in Example 1except that the amount of the solution B was changed to 374.0 parts andthe amount of the solution C was changed to 276.4 parts in “Formation ofresin layer sample A1” in Example 1. The total molar amount (A) of thehydroxyl groups of the acrylic resin prepolymer in the solution A was0.184 mol. The total molar amount (B) of the hydroxyl groups of thepolyol in the solution B was 0.92 mol. Thus, the ratio (B/A) was 5.

Example 4

An acrylic resin prepolymer A4 was synthesized in the same manner as inExample 1 except that, in “Synthesis of acrylic resin prepolymer A1” inExample 1, instead of 286.8 parts of hydroxyethyl methacrylate (HEMA),228.8 parts of hydroxyethyl methacrylate (HEMA) and 207.7 parts ofPLACCEL FM3 (manufactured by DAICEL CHEMICAL INDUSTRIES, LTD., compoundname: lactone-modified methacrylate, the number of carbon atoms in aside chain containing a hydroxyl group: 21) were used.

A resin layer sample A4 was obtained in the same manner as in Example 1except that, in “Formation of resin layer sample A1” in Example 1, 112parts of the solution of the above-described acrylic resin prepolymer A4(44.6%, hydroxyl value: 165) was used instead of 113 parts of thesolution of the acrylic resin prepolymer A1, the amount of the solutionB (PLACCEL 208, hydroxyl value: 138) was changed to 119.8 parts, and theamount of the solution C (Duranate TKA100) was changed to 110.69 parts.

The total molar amount (A) of the hydroxyl groups of the acrylic resinprepolymer in the solution A was 0.147 mol. The total molar amount (B)of the hydroxyl groups of the polyol in the solution B was 0.295 mol.Thus, the ratio (B/A) was 2.

Example 5

An acrylic resin prepolymer A5 was synthesized in the same manner as inExample 1 except that, in “Synthesis of acrylic resin prepolymer A1” inExample 1, instead of 286.8 parts of hydroxyethyl methacrylate (HEMA),228.8 parts of hydroxyethyl methacrylate (HEMA) and 207.7 parts ofPLACCEL FM3 (manufactured by DAICEL CHEMICAL INDUSTRIES, LTD., compoundname: lactone-modified methacrylate, the number of carbon atoms in aside chain containing a hydroxyl group: 21) were used; and, instead of313.2 parts of butyl methacrylate (BMA), 950.4 parts of CHEMINOX FAMAC6(manufactured by UNIMATEC CO., LTD., compound name:2-(perfluorohexyl)ethyl methacrylate, which contains fluorine atoms)were used.

A resin layer sample A5 was obtained in the same manner as in Example 1except that, in “Formation of resin layer sample A1” in Example 1, 113.6parts of the solution of the above-described acrylic resin prepolymer A5(44.0%, hydroxyl value: 89) was used instead of 113 parts of thesolution of the acrylic resin prepolymer A1, the amount of the solutionB (PLACCEL 208, hydroxyl value: 138) was changed to 64.6 parts, and theamount of the solution C (Duranate TKA100) was changed to 59.7 parts.

The total molar amount (A) of the hydroxyl groups of the acrylic resinprepolymer in the solution A was 0.08 mol. The total molar amount (B) ofthe hydroxyl groups of the polyol in the solution B was 0.16 mol. Thus,the ratio (B/A) was 2.

Example 6

A resin layer sample A6 was obtained in the same manner as in Example 5except that, in the formation of the resin layer sample A5 in Example 5,instead of 64.6 parts of the solution B (polyol, manufactured by DAICELCHEMICAL INDUSTRIES, LTD., PLACCEL 208, polycaprolactonediol), 44.7parts of C10DIOL (fluorine-atom-containing polyol, manufactured byExfluor Research Corporation, hydroxyl value: 199, hydroxyl groups areconnected to each other through a chain containing 10 carbon atoms) wereused.

The total molar amount (A) of the hydroxyl groups of the acrylic resinprepolymer in the solution A was 0.08 mol. The total molar amount (B) ofthe hydroxyl groups of the polyol in the solution B was 0.16 mol. Thus,the ratio (B/A) was 2.

Comparative Example 1

A resin layer sample B1 was obtained in the same manner as in Example 1except that, in “Formation of resin layer sample A1” in Example 1, theamount of the solution B was changed to 3.74 parts and the amount of thesolution C was changed to 48.37 parts. The total molar amount (A) of thehydroxyl groups of the acrylic resin prepolymer in the solution A was0.184 mol. The total molar amount (B) of the hydroxyl groups of thepolyol in the solution B was 0.009 mol. Thus, the ratio (B/A) was 0.05.

Comparative Example 2

A resin layer sample B2 was obtained in the same manner as in Example 1except that, in “Formation of resin layer sample A1” in Example 1, theamount of the solution B was changed to 1116 parts and the amount of thesolution C was changed to 734 parts. The total molar amount (A) of thehydroxyl groups of the acrylic resin prepolymer in the solution A was0.184 mol. The total molar amount (B) of the hydroxyl groups of thepolyol in the solution B was 2.75 mol. Thus, the ratio (B/A) was 15.

Comparative Example 3 Synthesis of Acrylic Resin Prepolymer B3

A monomer solution composed of 91.0 parts of hydroxyethyl methacrylate(HEMA, the number of carbon atoms in a side chain containing a hydroxylgroup: 3) serving as monomers providing short side chain hydroxylgroups, 660.8 parts of PLACCEL FM3 (manufactured by DAICEL CHEMICALINDUSTRIES, LTD., compound name: lactone-modified methacrylate, thenumber of carbon atoms in a side chain containing a hydroxyl group: 21),488.4 parts of isobornyl methacrylate (IBMA), 27 parts of apolymerization initiator (benzoyl peroxide, BPO), and 60 parts of butylacetate was charged into a dropping funnel and dropped into 300 parts ofbutyl acetate that was heated to 110° C. and being stirred over threehours under nitrogen flow to polymerize the monomers. Furthermore, asolution composed of 135 parts of butyl acetate and 3 parts of BPO wasdropped to this reaction solution over an hour to complete the reaction.The reaction solution was always maintained at 110° C. and being stirredduring the reaction. As a result, an acrylic resin prepolymer B3 wassynthesized. The content ratio (molar ratio) of long side chain hydroxylgroups to short side chain hydroxyl groups was 2.

Formation of Resin Layer Sample B3

The following solution C was added to the following solution A. Theresultant mixture was defoamed for 10 minutes under a reduced pressure.The thus-prepared solution was cast onto a polyimide film having athickness of 90 μm and cured at 85° C. for an hour and at 130° C. for 30minutes. Thus, a resin layer sample B3 having a thickness of 40 μm wasobtained.

Solution A (solution of the above-described acrylic resin prepolymer B3,45.2%, hydroxyl value: 97): 110.5 parts

Solution C (isocyanate, manufactured by Asahi Kasei ChemicalsCorporation, Duranate TKA100, compound name: hexamethylenediisocyanate-based polyisocyanurate): 21.7 parts

Comparative Example 4

A resin layer sample B4 for a protective layer was obtained in the samemanner as in Example 1 except that, in “Formation of resin layer sampleA1” in Example 1, instead of 149.6 parts of the solution B (polyol,manufactured by DAICEL CHEMICAL INDUSTRIES, LTD., PLACCEL 208,polycaprolactonediol, hydroxyl groups are connected to each otherthrough a chain containing about 42 carbon atoms), 1.15 parts ofethylene diol (hydroxyl value: 1806, hydroxyl groups are connected toeach other through a chain containing 2 carbon atoms) were used. Thetotal molar amount (A) of the hydroxyl groups of the acrylic resinprepolymer in the solution A was 0.184 mol. The total molar amount (B)of the hydroxyl groups of the polyol in the solution B was 0.037 mol.Thus, the ratio (B/A) was 0.2.

Comparative Example 5

An acrylic resin prepolymer B5 was synthesized in the same manner as inExample 5 except that, in the synthesis of the acrylic resin prepolymerA5 in Example 5, the amount of hydroxyethyl methacrylate (HEMA) waschanged from 228.8 parts to 95.3 parts and the amount of PLACCEL FM3(manufactured by DAICEL CHEMICAL INDUSTRIES, LTD.) was changed from207.7 parts to 692.3 parts; and, as in the synthesis of the acrylicresin prepolymer A5, CHEMINOX FAMAC6 (manufactured by UNIMATEC CO.,LTD., compound name: 2-(perfluorohexyl)ethyl methacrylate, whichcontains fluorine atoms) was used instead of butyl methacrylate (BMA).The content ratio (molar ratio) of long side chain hydroxyl groups toshort side chain hydroxyl groups was 2.

A resin layer sample B5 was obtained in the same manner as inComparative example 3 except that, in “Formation of resin layer sampleB3” in Comparative example 3, instead of 110.5 parts of the solution ofthe acrylic resin prepolymer B3, 111.2 parts of a solution of theabove-described acrylic resin prepolymer B5 (44.9%, hydroxyl value: 71)were used; and the amount of the solution C was changed from 21.7 partsto 15.1 parts.

Evaluation

The resin layer samples in Examples and Comparative examples weremeasured in terms of elastic modulus, recovery proportion, Martenshardness, and dynamic contact angle (advancing contact angle). Theresults are summarized in Table 1 below.

A FISCHERSCOPE HM2000 (manufactured by Fischer Instruments K.K.) wasused as a measurement apparatus. Each resin layer sample formed byapplying a resin to a polyimide film and polymerizing the resin wasfixed on a slide glass with an adhesive agent and placed in themeasurement apparatus. The resin layer sample was subjected to anincreasing load up to 0.5 mN over 15 seconds at room temperature (23°C.) and the resin layer sample was held under the load of 0.5 mN for 5seconds. At this time, the maximum displacement of the resin layersample was defined as h1. After that, the load was decreased to 0.005 mNover 15 seconds and the resin layer sample was held under the load of0.005 mN for a minute. At this time, the displacement of the resin layersample was defined as h2. The recovery proportion [(h1−h2)/h1] was thencalculated. In addition, the Martens hardness and the elastic moduluswere determined from a load displacement curve obtained at this time.

Scratching Resistance Test

The resin layer samples obtained above were evaluated in terms ofresistance to scratching by the following method.

Each of the polyimide films on which the resin layer samples wereformed, the polyimide films being obtained above, was affixed to thesurface of a fixing roller and 10,000 paper sheets were passed throughthe fixing device. After these paper sheets were passed, the presence orabsence of paper edge scratches in the resin layer sample was visuallyinspected. The fixing device used was a DocuCentre C2101 (trade name,manufactured by Fuji Xerox Co., Ltd.).

The evaluation was performed in accordance with the following criteria.

Good: Absence of scratches

Fair: Presence of shallow scratches having a depth of 0.5 μm or less

Poor: Presence of scratches having a depth of more than 0.5 μm

Releasability Test

The resin layer samples obtained above were evaluated in terms ofreleasability by the following method.

Each of the polyimide films on which the resin layer samples wereformed, the polyimide films being obtained above, was affixed to thesurface of a fixing roller and 10,000 paper sheets were passed throughthe fixing device (the same fixing device as that used above but apeeling claw was removed). In such a configuration where the peelingclaw was not used, the samples in which 10,000 paper sheets were passedwere evaluated as “Good” and the samples in which 10,000 paper sheetswere not passed were evaluated as “Poor”.

Evaluation Test in Terms of Removal Rate of Scratch

The resin layer samples obtained above were evaluated in terms ofremoval rate of a scratch by the following method.

Each of the resin layer samples obtained above was set to a frictiontester (trade name: TRIBOGEAR, manufactured by Shinto Scientific Co.,Ltd.). A sapphire needle was run for 1 cm on the resin layer sampleunder a load of 60 gram-weight to form a scratch in the surface of theresin layer sample. The time for which the scratch was no longervisually recognized was measured.

The evaluation was performed in accordance with the following criteria.

Excellent: the scratch disappeared within 10 seconds

Good: the scratch disappeared within 60 seconds

Fair: the scratch disappeared within 2 hours

Poor: the scratch remained after 2 hours had elapsed

TABLE 1 Dynamic Ratio of (advancing) Scratching Removal [long sideElastic Recovery Martens contact resistance Releasability rate ofchain]/[short modulus proportion hardness angle test test scratch Unitside chain] (B/A) % % N/mm² Degree — — — Example 1 0 2 93 99 2.6 91 GoodPoor Excellent Example 2 0 0.2 76 94 20 93 Good Poor Good Example 3 0 595 99 1.6 90 Good Poor Excellent Example 4 0.25 2 94 98 2.3 91 Good PoorExcellent Example 5 0.25 2 62 92 4.8 108 Good Good Good Example 6 0.25 280 91 6.5 116 Good Good Excellent Comparative 0 0.05 49 60 102 91 PoorPoor Poor example 1 Comparative 0 15 100 99 0.5 90 Fair Poor Excellentexample 2 Comparative 2 — 42 56 108 92 Poor Poor Poor example 3Comparative 0 0.2 60 45 148 91 Poor Poor Poor example 4 Comparative 2 —58 92 2.4 107 Good Good Fair example 5 “(BA)” in Table 1 represents aratio of the total molar amount (B) of hydroxyl groups contained in allthe polyols used for polymerization to the total molar amount (A) ofhydroxyl groups contained in all the acrylic resins used for thepolymerization.

Table 1 above indicates the following facts.

In Examples 1 to 6, excellent resistance to scratching and a highremoval rate of a scratch are achieved.

In Comparative example 2, although the removal rate of a scratch ishigh, since the sample is too soft and hence it is substantiallydifficult to use the sample.

Comparison between Example 5 in which the acrylic resin containsfluorine atoms and Comparative example 5 shows that the sample inExample 5 has a higher elastic modulus.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

1. A resin material used for a member for an image forming apparatus,the resin material comprising a polymer, wherein the polymer is formedby polymerization of at least one acrylic resin in which a content ratio(molar ratio) of hydroxyl groups of side chains each containing 10 ormore carbon atoms to hydroxyl groups of side chains each containing lessthan 10 carbon atoms is less than 1/3 (the acrylic resin may contain nohydroxyl group of a side chain containing 10 or more carbon atoms); atleast one polyol that contains a plurality of hydroxyl groups in whichall the plurality of hydroxyl groups are connected together through achain containing 6 or more carbon atoms; and an isocyanate, with apolymerization ratio of about 0.1 or more and about 10 or less, thepolymerization ratio being a ratio (B/A) of a total molar amount (B) ofhydroxyl groups contained in all the polyols used for the polymerizationto a total molar amount (A) of hydroxyl groups contained in all theacrylic resins used for the polymerization.
 2. The resin materialaccording to claim 1, wherein the at least one polyol contains afluorine atom.
 3. The resin material according to claim 1, wherein theat least one acrylic resin contains a fluorine atom.
 4. The resinmaterial according to claim 2, wherein the at least one acrylic resincontains a fluorine atom.
 5. The resin material according to claim 1,wherein the resin material has a dynamic contact angle (advancingcontact angle) of about 90° or more and about 150° or less.
 6. The resinmaterial according to claim 2, wherein the resin material has a dynamiccontact angle (advancing contact angle) of about 90° or more and about150° or less.
 7. The resin material according to claim 3, wherein theresin material has a dynamic contact angle (advancing contact angle) ofabout 90° or more and about 150° or less.
 8. The resin materialaccording to claim 4, wherein the resin material has a dynamic contactangle (advancing contact angle) of about 90° or more and about 150° orless.
 9. An endless belt for an image forming apparatus, the endlessbelt comprising the resin material according to claim 1 on asubstantially belt-shaped base member.
 10. A roller for an image formingapparatus, the roller comprising the resin material according to claim 1on a substantially tubular base member.
 11. An image fixing devicecomprising: a first rotational body; and a second rotational body thatis in contact with the first rotational body to form a nipping region inwhich a recording medium is nipped between the first rotational body andthe second rotational body, wherein at least one of the first rotationalbody and the second rotational body is the endless belt for an imageforming apparatus according to claim
 9. 12. An image fixing devicecomprising: a first rotational body; and a second rotational body thatis in contact with the first rotational body to form a nipping region inwhich a recording medium is nipped between the first rotational body andthe second rotational body, wherein at least one of the first rotationalbody and the second rotational body is the roller for an image formingapparatus according to claim
 10. 13. An image forming apparatuscomprising: an electrostatic latent image holding body; an electrostaticlatent image forming section that forms an electrostatic latent image ona surface of the electrostatic latent image holding body; a developingsection that develops the electrostatic latent image by using toner toform a toner image; a transfer section that transfers the toner imageonto a recording medium; and the image fixing device according to claim11 that fixes the toner image on the recording medium.
 14. An imageforming apparatus comprising: an electrostatic latent image holdingbody; an electrostatic latent image forming section that forms anelectrostatic latent image on a surface of the electrostatic latentimage holding body; a developing section that develops the electrostaticlatent image by using toner to form a toner image; a transfer sectionthat transfers the toner image onto a recording medium; and the imagefixing device according to claim 12 that fixes the toner image on therecording medium.
 15. An image forming apparatus comprising: anelectrostatic latent image holding body; an electrostatic latent imageforming section that forms an electrostatic latent image on a surface ofthe electrostatic latent image holding body; a developing section thatdevelops the electrostatic latent image by using toner to form a tonerimage; an intermediate transfer body that includes the endless belt foran image forming apparatus according to claim 9; a first transfersection that transfers the toner image on the electrostatic latent imageholding body onto the intermediate transfer body; and a second transfersection that transfers the toner image on the intermediate transfer bodyonto a recording medium.
 16. An image forming apparatus comprising: anelectrostatic latent image holding body; an electrostatic latent imageforming section that forms an electrostatic latent image on a surface ofthe electrostatic latent image holding body; a developing section thatdevelops the electrostatic latent image by using toner to form a tonerimage; an intermediate transfer body that includes the roller for animage forming apparatus according to claim 10; a first transfer sectionthat transfers the toner image on the electrostatic latent image holdingbody onto the intermediate transfer body; and a second transfer sectionthat transfers the toner image on the intermediate transfer body onto arecording medium.
 17. An image forming apparatus comprising: anelectrostatic latent image holding body; an electrostatic latent imageforming section that forms an electrostatic latent image on a surface ofthe electrostatic latent image holding body; a developing section thatdevelops the electrostatic latent image by using toner to form a tonerimage; a recording medium transport body that transports a recordingmedium and includes the endless belt for an image forming apparatusaccording to claim 9; and a transfer section that transfers the tonerimage on the electrostatic latent image holding body onto the recordingmedium on the recording medium transport body.
 18. An image formingapparatus comprising: an electrostatic latent image holding body; anelectrostatic latent image forming section that forms an electrostaticlatent image on a surface of the electrostatic latent image holdingbody; a developing section that develops the electrostatic latent imageby using toner to form a toner image; a recording medium transport bodythat transports a recording medium and includes the roller for an imageforming apparatus according to claim 10; and a transfer section thattransfers the toner image on the electrostatic latent image holding bodyonto the recording medium on the recording medium transport body.